This invention generally relates to diffused aeration systems used for treating polluted liquids. More particularly, the invention relates to an orifice device for an aeration system in which a plurality of fluid injection pipes, immersed in a body of polluted liquid, are connected to a fluid manifold while the orifice devices themselves are not so submerged.
In one known aeration system, a horizontal fluid manifold is installed above the body of liquid to be treated. Short sections of pipe or nipples, threaded into the manifold, extend horizontally from the manifold across the surface of the polluted liquid. On to each nipple is threaded an orifice fitting which has an orifice plate clamped between a pair of flanges. One end of a second nipple is threaded into the downstream side of each orifice fitting, and the opposite end is threaded into the side connection of a standard tee-joint fitting. The centerline of the run of the tee-joint (i.e., the section having opposed, open, threaded ends) is vertically disposed and perpendicular to the centerline of the second nipple. A plug is threaded into the upper open end of each tee-joint. A fluid injection pipe, connected to the bottom open end of each tee-joint, extends downwardly from the tee-joint into the polluted liquid. The bottom end of each fluid injection pipe is provided with a diffuser head which facilitates the diffusion of oxygen into the liquid.
In another known aeration system, a third nipple is threaded into the upper open end of the tee-joint, and the top of the nipple is closed by a removeable pipe cap.
In these known aeration systems, removal of the plug or pipe cap sealing the tee-joint at the top of each fluid injection pipe permits access into the interior of the injection pipe for cleaning or maintenance.
During operation, pressurized oxygen-containing gas flows sequentially through the fluid manifold, the series of nipples, the orifice plates and the second nipples, and then through the tee-joints where the flow direction is changed from horizontal to vertical. The gas then flows down the fluid injection pipes, through the diffuser heads, and into the polluted liquid.
As a consequence of their tortuous gas flow paths, known aeration systems have high pressure drops which limit the allowable penetration of the fluid injection pipes into the polluted liquid. The high pressure drops also limit the amount of oxygen that may be diffused into the liquid. In those known systems wherein all the injection pipes penetrate the liquid to a particular depth, the high pressure drops require an increased expenditure of energy to force the gas through the systems and into the polluted liquid.